Introduce a new kfunc bpf_kernfs_read_xattr, which can read xattr from kernfs nodes (cgroupfs, for example). The primary users are LSMs, for example, from systemd. sched_ext could also use xattrs on cgroupfs nodes. However, this is not allowed yet, because bpf_kernfs_read_xattr is only allowed from LSM hooks. The plan is to address sched_ext later (or in a later revision of this set). Song Liu (4): kernfs: Add __kernfs_xattr_get for RCU protected access bpf: Introduce bpf_kernfs_read_xattr to read xattr of kernfs nodes bpf: Mark cgroup_subsys_state->cgroup RCU safe selftests/bpf: Add tests for bpf_kernfs_read_xattr fs/bpf_fs_kfuncs.c | 33 ++++ fs/kernfs/inode.c | 14 ++ include/linux/kernfs.h | 2 + kernel/bpf/verifier.c | 5 + .../selftests/bpf/prog_tests/kernfs_xattr.c | 145 ++++++++++++++++++ .../selftests/bpf/progs/kernfs_read_xattr.c | 117 ++++++++++++++ .../selftests/bpf/progs/read_cgroupfs_xattr.c | 60 ++++++++ 7 files changed, 376 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/kernfs_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/kernfs_read_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c -- 2.47.1
